JPS58219438A - Spectrochemical analysis device using laser light - Google Patents

Abstract

PURPOSE:To make it possible to set the distance between the surface of a sample and a spectroscope arbitrarily, by providing a condenser lens, which makes light from a sample ring shaped parallel light, and a spectroscope optical system, and making laser light and the light from the sample in parallel between the lens and the system on the same axis. CONSTITUTION:A condenser lens 32 converges laser light 13 on a sample 16 and makes light 33 emitted from the sample ring shaped parallel light, which is propagated in the reverse direction with respect to the laser light 13 on the same axis. A ring shaped concave mirror 34 and a spectroscope optical system including expandable mirror tubes 40 and 40a, which guide the light 33 from the sample that is made to be the ring shaped parallel light to a spectroscope 22, are provided. The light 33 from the sample can be efficiently guided to the spectroscope by the adjustment of the mirror tubes 40 and 40a, regardless of the length of the distance between the sample 16 and the spectroscope 22. Thus the highly accurate, general purpose device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser emission spectrometer, which is particularly suitable for direct analysis of bath iron, molten steel, and molten slag. The present invention relates to an improvement in a laser emission spectrometer that spectrally analyzes light emitted from the surface of a sample using a spectrometer.

When a strong pulsed laser beam is irradiated onto the surface of a sample, energy is locally injected, causing melting and evaporation, and further exciting the vapor, turning it into plasma and emitting light. A laser emission spectrometer that disperses this light with a spectrometer and measures the spectral line intensity of the target element using photographic film, a photomultiplier tube, a photodiode, etc., determines the content of the target element. Are known.

As shown in FIG. 1, an optical system used in a laser emission spectrometer using laser light as an excitation source includes a laser emitting section 12 and a laser beam irradiated from the laser emitting section 12 on a sample 16. A laser irradiation system 10 consisting of a condensing lens 14 for converging the light on the surface of the sample 16, a spectrometer optical system 20° for guiding the light emitted from the surface of the sample 16 to the spectroscope 22, and a spectroscope consisting of the spectroscope 22. As shown in FIG. A laser irradiation system 10 consisting of a right-angle prism 24 for changing the direction of the laser beam, and a condensing lens 14 for laser light for converging the laser beam whose direction has been changed by the right-angle prism 24 onto the surface of a sample 16 made of molten steel or the like. and a condensing lens 26 for the sample emitted light to convert the light emitted from the surface of the sample 160 into light that propagates coaxially and in the opposite direction to the laser beam. The sample emitted light is collected using a spectrometer (
The laser beam irradiation system 10 and the spectrometer system 18 have a beam slit 28 with a laser beam transmitting part formed in the center and a spectrometer system 18 for guiding the laser beam to a laser beam (not shown).
A device in which 8 is made coaxial from the middle has been developed. According to the former, it is effective for sample 16 with a smooth surface, but
It is necessary to strictly control the position where the sample 16 is placed. father,
According to the latter, even if the position of the sample 16 changes slightly, the light emitted from the sample 16 can be guided to the spectrometer 22. However, in any optical system, if the distance between the sample 16 and the spectrometer 22 changes, the sample 1
The light emitted from the sample 16 cannot be efficiently guided to the spectrometer 22, and the distance between the sample 16 and the spectrometer 22 cannot be arbitrarily set.

The present invention was developed in order to solve the above-mentioned conventional drawbacks, and the distance between the sample surface and the spectrometer can be arbitrarily set, thus eliminating various restrictions on the installation of the spectrometer in a factory, etc. An object of the present invention is to provide a highly versatile laser emission spectrometer that can be applied to any location.

The present invention provides a laser emission spectrometer that uses a spectrometer to perform spectroscopic analysis of light emitted from a sample surface when a laser beam is irradiated from a laser emitting section, which includes converging the laser beam onto the sample surface, and a condenser lens for converting the light emitted from the sample surface into an annular parallel ray that propagates coaxially and in the opposite direction to the laser beam; and a one-annular consonant ray, at least a part of which is disposed outside the laser beam. A spectrometer optical system is provided to guide the sample emitted light into a spectroscope, and the laser beam and the sample emitted light between the condenser lens and the spectrometer optical system are coaxial and parallel to each other, The above objective has been achieved.

The present invention uses an optical crystal CaF2 that transmits vacuum ultraviolet light.

This was done based on the fact that if the material is highly pure, it is possible to focus the laser light.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In this embodiment, as shown in FIG. 22, the laser emission spectrometer is equipped with a right-angle prism 24 for changing the irradiation direction of the laser beam 13 emitted from the laser beam ff1l12, and a laser beam 13 on the output side of the right-angle prism 24 as a sample. A condensing lens 32 for converging the light emitted from the sample surface onto the surface of the sample 16 into an annular parallel light ray 33 that propagates coaxially and in the opposite direction to the laser beam 13;
a spectrometer optical system 20 consisting of a toric concave mirror 34 for imaging the sample emitted light 33, which has been converted into one circular consonant beam and is placed outside the laser beam 13, onto the entrance slit 36 of one spectrometer 22; , and a spectrometer 22.

A photodetector 38 for detecting the intensity of the spectral lines separated by the spectrometer 22 is arranged behind the spectrometer 22, and the distance between the condenser lens 32 and the spectrometer optical system 20 is variable. A lens barrel 4o having a mating portion 40a formed in the intermediate portion is provided for this purpose.

The laser emitting unit 12 emits a pulsed laser beam having a predetermined output and pulse width, for example, a wavelength of 0.69μ.
A ruby laser with a wavelength of 1.05 to 1.06 μm and an infrared laser with a wavelength of 1.05 to 1.06 μm are used. A mode locking mechanism is incorporated into this laser emitting unit 12, and the mode of the laser beam 13 is set to a Gaussian distribution type TER'fo.

It is desirable to fix the mode.

The right angle prism 24 is for aligning the optical axes of the laser irradiation system 10 and the spectrometer system 18.

This can be omitted if the laser emitting section 12 is installed perpendicularly to the surface of the sample 16.

The condensing lens 32 converges the laser beam 13 onto the surface of the sample 16 at its focal point, and propagates the light emitted by the plasma formed on the sample surface in a coaxial direction opposite to that of the laser beam. .

As this condensing lens 32, a convex lens made of ordinary optical glass is used. In particular, when detecting a spectrum in the vacuum ultraviolet region, highly purified CaF2, MgF is used.
Optical crystals such as z, LiF, BaF*, StO, etc. are used.

The annular concave mirror 34 of the spectrometer optical system 200 is disposed on the outer side of the same axis of the laser beam 13 so as not to be irradiated with the laser beam 13 from behind. This annular concave mirror 34 converts the light 33 emitted from the sample 16 and parallelized by the condensing lens 32 to the entrance slit 3 of the spectrometer 22.
It has a curvature of 6. In the embodiment shown in FIG. 3, one annular concave mirror 34 is used, but for example, as in the first modification shown in FIG. In addition, depending on the wavelength of the spectrum to be measured, a beam splitter 44 and a convex lens 46 may be combined as in the second modification shown in FIG. 5. It is possible.

As the photodetector 38, for example, a photomultiplier tube, a photodiode, a photographic film, etc. are used.

In preparation for detecting a spectrum in the vacuum ultraviolet region, the lens barrel 40 has an argon atmosphere between the sample 16 and the condenser lens 32, and a vacuum between the condenser lens 32 and the spectrometer 22, or an argon gas introduction part 40b for creating an argon atmosphere between the sample 16 and the spectrometer 22;
Optical glass 48 that seals the laser beam introduction part, spectrometer 2
A vacuum sealing glass 50 made of CaF or the like is provided to seal the rear stage of the second entry loss slit 36.

The action will be explained below.

First, the fitting portion 40a'i of the lens barrel 40 including the condenser lens 32 and the spectrometer optical system 2o is adjusted, and the position is set so that the surface of the sample 16 comes to the focal point of the condenser lens 32.

At this time, an existing length measuring needle may be used. Next, the laser emitting unit 12 is activated to emit laser light 13 with a predetermined intensity and pulse width. The laser beam 13 is transmitted through a right angle prism 2
4 into the condenser lens 32 and focused on the surface of the sample 16. The laser irradiated portion of the sample 16 is instantaneously turned into plasma and emits light. This light is transmitted through the condensing lens 3
2, it becomes an annular parallel ray 33, and the annular concave mirror 34 of the 5-spectroscope optical system 20 creates a losslist 36 that enters 1 spectrometer 220.
guided by. Inside the spectrometer 22, light is dispersed by a diffraction grating, prism, etc., and the spectral line intensity of the measurement target is read by a photodetector 3B, and the data is processed in a normal manner and analyzed. .

With the device as shown in the previous example, a diameter of 5Qmi
Using a high-purity CaF211ij condenser lens 32 with a focal length of 1501 m and an argon atmosphere between the sample 16 and the vacuum sealing glass 50, the sample 16 made of an Fe-82 element alloy was exposed to a wavelength of 1.06 μm, an output of 2 J, and a pulse width. 15
271 obtained when irradiated with n5ea laser light
．． 4 nm Fe spectral line intensity and 180.7
When the S spectral line intensity in nm was measured while changing the distance between the sample 16 and the spectrometer optical system 20, the results shown in FIG. 6 were obtained.

As is clear from the figure, considering that the laser output varies by about 10%, the intensity of the spectral lines in the two samples 16
It is clear that it does not depend on the distance between and the spectrometer optics 20.

As explained above, according to the invention, measurements with a high degree of n can be performed regardless of the distance between the sample and the spectrometer. Therefore, it can be applied to places where there are various restrictions on the installation of spectrometers, such as in factories, and has the excellent effect of reducing versatility.

[Brief explanation of drawings]

Fig. 1 is a front view showing the arrangement of the laser irradiation system and spectrometer system in one example of a conventional laser emission spectrometer, and Fig. 2 shows the arrangement of the laser irradiation system and spectrometer system in another example. 3 is a sectional view showing the configuration of an embodiment of the laser emission spectrometer according to the present invention. FIG. 4 is a front view showing the arrangement of the spectrometer optical system in the first modification, and FIG. Figure 5 is
The same (a front view showing the arrangement of the spectrometer optical system divided into the second modification example, FIG. 6 shows the Fe,
FIG. 2 is a diagram showing an example of the relationship between the spectral line intensity of S and the distance between the sample and the spectrometer optical system. ]0... Laser irradiation system, 12... Laser emitting unit. 13... Laser light, 16... Sample, 18... Spectrometer system, 20... Spectrometer optical system, 22... Spectrometer, 3
2... Condensing lens, 33... Annular sample emission light, 3
4... Annular concave mirror, 36... Rothrich, 38
...Photodetector. 42...Plane mirror, 44...Beam splitter, 46
···convex lens. Agent Takaya Ron (and 1 other person) (11) Fig. 1 Fig. 2 Fig. 1:2::2-2---16 Fig. 3] 204- Fig. 4 Fig. 5

Claims (1)

[Claims] (In a laser emission spectrometer that uses a spectrometer to spectrally analyze the light emitted from the sample surface when a laser beam is irradiated from the laser emitting part, the laser beam is focused on the sample surface and a condensing lens for converting the light emitted from the laser beam into an annular parallel beam that propagates coaxially and in the opposite direction to the laser beam; A spectrometer optical system is installed to guide the sample emitted light to the spectrometer so that the laser beam and sample emitted light between the converging lens and the spectrometer optical system are coaxial and parallel to each other. A laser emission spectrometer featuring: